Many chemical processes are known which cause fouling of the process equipment in use in these chemical processes. For example, during oligomerisation or polymerization processes product mixtures consisting of olefins, including alpha-olefins, C10+ olefins and polymer including polyethylene may be produced. In the case of a tetramerisation or trimerisation process, for example, ethylene is catalytically converted into a product mixture consisting primarily of 1-octene and 1-hexene. Typically, the product mixture will consist of at least 30% by mass 1-octene and 1-hexene respectively. However, during this reaction, by-products consisting of light ends, C10+ olefins and polyethylene are also formed. Polyethylene is therefore formed as a by-product and although a large percentage of the polyethylene exits the reactor as a slurry with the product mixture, the remaining polyethylene coats the reactor surfaces. This fouling layer builds up over time and eventually the reactor requires cleaning.
In the case of ethylene oligomerisation reactors, the cleaning of the reactors has traditionally been effected by hot washing with a solvent at elevated temperatures. Although highly effective, hot washing has numerous undesirable consequences including thermal stress to the vessel, long cleaning times, complicated agitator design and complicated vessel internals.
Although hydroblasting of a process vessel, such as an oligomerisation reactor, is a simple alternative cleaning method, the use of water is very often undesirable as it may be a poison to any catalyst used in the vessel. In addition, the time taken to open a process vessel for cleaning is often also prohibitive.